In a solid-state image pickup device, from a unit pixel including a photoelectric conversion section, an output signal substantially linear with respect to the amount of charges stored in the photoelectric conversion section by photoelectric conversion is obtained. Then, the dynamic range of the solid-state image pickup device is uniquely determined by the amount of charges (amount of saturated charges) that the unit pixel can store in the photoelectric conversion section and the noise level. That is, the lower limit of the output level of the solid-state image pickup device is limited by the noise level, and the upper limit thereof is limited by the saturation level of the photoelectric conversion section. As a result, the dynamic range of the solid-state image pickup device is uniquely determined by the amount of saturated charge and the noise level of the photoelectric conversion section.
In the past, as a technology for expanding the dynamic range of the solid-state image pickup device, the following three methods have been known.
(1) Time division method: expand a dynamic range by capturing a plurality of images with different sensitivities due to a difference in storing time by time division and combining the plurality of images captured by time division (see, for example, Patent Literature 1)(2) Spatial division method: expand a dynamic range by providing a plurality of pixels with different sensitivities and combining a plurality of images captured by the plurality of pixels with different sensitivities (see, for example, Patent Literature 2)(3) In-pixel memory addition method: expand a dynamic range by providing, in each pixel, a memory that stores charges overflowed from a photoelectric conversion section to increase the amount of charges that can be stored in a period of time of exposure (see, for example, Patent Literature 3)